Process for phenylimidazolino [1, 2-alpha]piperidines



Q1PRoeEssEoRPineal nvnnAzotlNo' 1 12;: 1 [LZ I JPE I N SM I f Seymour Shapiro, Hastings on Hudson, Freed 1 l man, Bronxville, and Harold Soloway ngers, .Yr. I

No. Drawing. Application Alarms S'eiialNo'.727 ,259-

This invention is concerned with a. novel pr'ocess for the preparation of 2 phenylimidazolin) [l.2 alpiperidirles II and related compounds; ,jIn particular, it is the object oi this invention to p'r'epafe 'compoundspf the s t ructuref l IV V In the reaction, the Z-aminopyridine reacts in its imino form at the azine nitrogen with styrene oxide to yield the 2 (Z-imino-1,Z-dihydro-l-pyridine)-1-pheny1ethanol (I). These compounds are converted to their hydro chlorides and-are reduced under hydrogen with rhodium wherein R is hydrogen and methyl, as intermediates in on carbon asa/catalyst to yield the 2-(2-arnino-1- piperidine)-1-phenylethanol hydrochloride (II). (For structure proof of the compounds and the importance of the use of the hydrochloride of I inthe reduction, refer to:Exar'nple 4"below.) Conversion to the chloride III, 2-(2-amino-1-piperidine)-1-phenylethy1- chloride hydrochloride, is effected bytreatme'nt of lI withthionyl chloride. The resultant chloride III is dehydrohalogenated and: eyclized to the corresponding 2-phenylimidazolino- [l,2-a]piperidine IV by treatment in -an'organic solvent oramixed'iaqueous organic solvent in the presenceof an acid. acceptor such as "sodium .carbonate or sodium h ydrbxide. Other alkaliine'tal hydroxides or carbonates as well as strong'organic bases c'ari also function as the acid I acceptors.

agents. Additional and useful variants applicable-to the p, eparation' of new and useful organiccompounds-will be apparent" to those'sk illed in the art, I I I I I The synthetic route used in the preparation of these important intermediates is shown-in Scheme I.

. permitted to crystallize.

The compounds. in the series I-IV show interesting pharmacological properties particularly as diuretics, antiinflammatory agents anduganglionic blocking agents.

The compounds herein described all have at least one asymmetric carbon atom] Thins, I has one,"a nd where R== CH II, III "and 'IV have three. ---"I'he exact stereochernistry of; the-groups has not been established; and the various stereochemicalforms are to bee-considered within the purview ofrthisinv ention, I II I flhe process .,and compounds f this invention will be nio reflcle'arly understoodfrom a consideration of the fo llowing specificexamples yvhich are given for the pu pose ffillustratiotionly and are not to be construed as limitlng thescopefof the invention in any way. Temperal 'e ib e aw arsin I I EXAMPLE 251i? 2-(2-ihiifi'o-3 methyld ,Z-riihydropyridine'i-J -""pheriylethan0l A mixture of 24.0 g. (0.2 mole) of styrene oxide and 32.4 g .(0.' 3 molel of, 2 -amino-3emethylpyridine .was together on. asteam- -bath in a flask fitted with a was t'aken up in 200 ml. .otlhoilingethanol, filtered and After refrigerating 3 hours filtration gave 22.4 g. (49%) of product, melting at 158 -161' C. I

Recrystallization from isopropyl alcohol, then acetonitrile, gave a 40% yield of product, melting at 166-167.

Analysis.'Ca1cd. for C H N O: C, 73.7; H, 7.1; N,

Found: C, 73.7; H, 6.7; N; 11.8.

A 'monohydrochloride prepared in ethanol and recrystallized. from a mixture of acetonitrile and n-propanol,

5 melted at 185-186. I a

:, A monopicrate prepared and recrystallized (ethanol).

mfiltedfat 136-437.".

Pgtented May 17, 19 I con'denserlf At the'efnd of this period,.the mixture There was similarly prepared from 2-amino-4-methylpyridine, 2 (2-imino-4-methyl-1,2-dihydro-1-pyridine)- l-phenylethanol in 13% yield, M.P. 159-160 (ethanol).

Analysis.-Calcd. for C H N O: C, 73.7; H, 7.1; N, 12.3. Found: C, 73.6; H, 7.2; N, 12.4.

The compound was also characterized as its hydrochloride, M.P. 230-231 (ethanol).

There was similarly prepared from 2-amino-5-methylpyridine, 2-(2-imino-5-methyl-1 ,2-dihydro-1-pyridine) -1- phenylethanol in 26% yield, B.P. 184188 at 0.4 mm. The picrate of this compound was prepared, M.P. 243 d. (ethanol).

Analysis;Calcd. for C H N O N, 15.3. Found: N, 15.1.

There wassimilarly prepared from 2-arnino-6-methylpyridine, 2 Z-imino-G-methyl-1,2-dihydro-1-pyridine)-1- phenylethanol in 15% yield, B.P. 181-184 at 0.3 mm.

The picrate of this compound was prepared, M.P. 151-153".

Analysis.---Calcd. for C H N O C, 52.5; H, 4.2; N, 15.3.1 FoundrC, 52.4;H, 4.4; N, 15.3.

EXAMPLE 2 2- (Z-imino-I ,Z-dihydro-I pyridine -pheny [ethanol A mixture of 12.0 g. (0.1 mole) of. styrene oxide and 14.1 g. (0.15 mole) of 2-aminopyridine was heated on a steam bath with stirring for 6 hours. action mixture was taken up in 50ml. of boiling ethanol, filtered and allowed to cool. .After refrigerating for 3 hours, the crystalline product was filtered otf, yielding 7 g. melting at 165-166". Recrystallization from 200 ml. of ethyl acetate gave 5.5 g. (26%) melting at 166-169". Analysis.-Calcd. for .C H N C, 72.9; H, 6.6; N, 13.1. Found: C, 73.3; H, 6.8; N, 13.0. a

A monohydrochloride was prepared and recrystallized (isopropyl alcohol), M.P. 197-200 d.

Analysis.Calcd. for C H ClN O: C, 62.3; H, 6.0; N, 11.2. Foundz-C, 63.0; H, 6.1; N, 11.9.

i EXAMPLE 3 2-(2-amino-l-piperdine),-1-phenylethanol hydrochloride A 249 g. (0.01 mole) portion of 2-(2-imino-L2-dihydro-l-pyridine)-l-phenylethanol hydrochloride was dissolved in 225 ml. of ethanol and 2 g. of rhodium on carbon added. The mixture was shaken in a Parr hydrogenator at an initial pressure of 4 atmospheres of hydrogen until the calculated quantity of hydrogen was taken The viscous reup. After removal from the hydrogenator, filtration and removal of solvent, 25 g. of product was obtained which was recrystallized (methyl ethyl ketone and ethanol mixture), M.P. 184-l85.

i NE r r H H v r A 53 g. 0.25 mole) portionof Z-(Z-imino-LZ-dihydro-l-pyridine)-1-pheynlethanol was dissolved in 200 ml. of ethanol, 5 got 5% rhodium on carbon added and the mixture shaken in a Parr hydrogenator at an initial pres- N, 10.4. Found: C,61-.6; H, 8.8; N, 10.1.

in pressure was noted. On removing the reaction mixcure-from the hydrogenator a strong odor of ammonia was observed.

The catalyst was filtered 0E and the solvent distilled from the filtrate at diminished pressure, yielding a product which crystallized on standing: giving 51.5 g. melting at -60-62; recrystallized (hexane), M.P. 6264. A mixed melting point with an authentic sample of 2'-piperidine-1- phenylethanol (melting at 65-67") showed no change in melting point. r r

A hydrochloride prepared and recrystallized (acetonitrlle) meltedat 126-128.

Analyst-cared, for c,,n,,c N0= N, 5.8. Found N, 5.8. v j

A picrate prepared and recrystallized (ethanol), melted at 135-137".

Analysis.-Calcd.-for C H N O C, 52.5; H, 5.1; N, 12.9. Found: C, 52.9;H, 5.3; N, 13.0.

This reaction served to identify the mode of addition of the 2-amino-pyridines to styrene oxide, with the azine nitrogen attacking the oxide group.

EXAMPLE 5 2-(2-amino-3-methyl-1-piperidine) -1-pheriylethanol hydrochloride CHI .HCl

Analysis.-Calcd. for c,.,H,,c1N,o: 0,621; H, 8.6;

EXAMPLE 6 a Z-(Z-amino-I-pipenline)-1-phenylethyl chloride hydra chloride A 25.5 g. (0.1 mole) portion of 2-(2-amino-lpiperidine)1-phenylethanol hydrochloride was suspended in 250 ml. of anhydrous ether and 14.3 g. (0.12 mole) of thionyl chloride added over 30 minutes with stirring. After addition was complete, the ether was decanted from the gummy solid and the latter triturated with fresh dry ether, then filtered to give 25.6 g. of product which after recrystallization (acetonitrile) melted at l82-184.

Analysis.-Calcd. for C13H20C1QN31 C, 56.7; H, 7.3; N, 10.2; C1, 25.8. Found: C, 56.9; H, 6.6; N, 10.2; CI, 26.4. r

A monopicrate prepared and recrystallized (ethanol), melted at 127-1302 Analysis.'Calcd. for 0 11 0151 0 C, 48.8; H, 4.7. Found: C, 48.8; H, 4.3.

EXAMPLE 7 A 2-(2-amiri0-5-mezhyl-1-piperidine)-1-phenylethyl chloride sure of .4'atmospheres ofhydrogen. After 7 hours, 0.9

mole of hydrogen had been taken up and no further drop hydrochloride In a manner similar to that described in Example 6, 2-(2-amino-3-methyl-l-piperidine)r 1 -phenylethanol hydrochloride was converted by treatment :with thionyl chloride to the title compound in 25% yield, M.P. 215- 216 (methyl ethyl ketone-ethanol mixture).

AnalysisJ-Calcd. for C J I CI N N, 9.7. Found: N, 9.5. 1

A monopicrate prepared and recrystallized (ethanolwater mixture) melted at 98-99".

Analysis.Calcd. for C2uHg4ClN501: C, 49.9; H, 5.0; N, 14.5; C1, 25.0. Found: C, 49.6; H, 5.6; N, 13.7; C1, 25.0.

EXAMPLE 8 Z-phenylimidazolino [1,2 a ]piperidine Method A.-Sodium carbonate, 12.7 g. (0.12 mole), was suspended in 150 ml. of refluxing benzene. To this was added dropwise with stirring, a solution of 9.3 g. (0.03 mole) of 2-amino-1-(2-chloro-2-pheny1)-ethylpiperidine hydrochloride in 100 m1. of ethanol over 1.5 hours. The reaction mixture was refluxed with stirring for 13 hours, cooled, filtered and the solvent distilled from the filtrate. The residual oil was extracted with ether, 21 small amount of solid filtered oil and the ether evaporated from the filtrate to give 3.2 g. of oil which was distilled and yielded the product, boiling at 118-120 at 0.3 mm.

Analysis.-Calcd. for C H N N, 13.9. Found: N, 13.6.

A picrate prepared and recrystallized (ethanol) melted at 176-178".

Analysis-Called. for C H N O C, 52.9; H, 4.9; N,

Analysis.-Calcd. for C H ClN O C, 61.9; H, 5.7; N, 10.8. Found: C, 61.9; H, 5.6; N, 10.6.

Method B.-Sodium hydroxide, 4.0 g. (0.1 mole), was dissolved in 25 ml. of water and then added to 25 ml. of acetonitrile and a solution of 9.3 g. (0.03 mole) of 2- amino-l-(2-chloro-2aphenyl) ethylpiperidine hydroehloride in 50 ml. of 50% aqueous acetonitrile was admitted over 1 hour. Stirring was continued for a total of 15 hours after addition was complete.

At the end of this period, an additional 50 ml. of water was added and the acetonitrile distilled out to yield a dark residue. This was extracted with five 20 ml. portions of ether, the extracts dried over anhydrous magnesium sul- :fate, then filtered and distilled. After removal of the ether, 1.5 g. (25%) of product was obtained, boiling at 113-116 at 0.2 mm.

We claim: 1. The compound NH N where R is a member of the group consisting of hydrogen and methyl.

-2. The compound R OH where R is a member of the group consisting of hydrogen and methyl.

3. The compound 25 N: -CHr-ZH-.HC1

where R is a member of the group consisting of hydro gen and methyl. I

4. The compound where R is a member of the group consisting of hydrogen and methyl.

References Cited in the file of this patent 

4. THE COMPOUND 